Railway signaling apparatus



y 9, 1940- J. M. PELIKAN 2,207,108

RAILWAY S IGNALING APPARATUS Filed April 12, 1939 INVENTOR John M Pelz'lian BYQ'z HIS ATTORN EY Patented July 9, 1940 UNITED STATES RAILWAY SIGNALING APPARATUS John M. Pelikan, Pittsburgh, Pa, assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application April 1.2, 1939,- Serial No. 267,477

14 Claims.

My invention relates to railway signaling apparatus, and has particular reference to the organization of such apparatus into railway signaling systems of the type commonly termed automatic interlocking systems.

In systems of automatic interlocking hitherto proposed, priority of movement over the conflicting trafilc portions of track is usually granted to the track on which a train first occupies an approach section adjacent the conflicting. trafiic portion, and the established track priority is maintained as long as that approach section is occupied, even though the approach section for the other track becomes occupied. While this system of establishing and maintaining track priority is satisfactory in many instances, such system is undesirable in the event that trafiic movements over two conflicting tracks are so scheduled that trains from each track follow each other alternately over the conflicting trafiic portions, and the volume of traflic is such that two or more trains may occupy each approach section concurrently. Accordingly, an object of my present invention is the provision in an automatic interlocking system, of novel and improved means trafic movements are then so controlled as to.

permit trains on each track to proceed alternately over the conflicting track portions.

Apparatus embodying my invention is particularly well adapted for, but not limited thereto, controlling the movements of trains on subway, elevated or surface systems where a large number of trains or individual cars are operated with very close headways.

Other objects and advantages of my invention will appear as the specification progresses.

I shall described one form of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic view showing a preferred form of apparatus embodying my invention.

Referring to the drawing, the reference character 2 designates a first stretch of railway track over which traffic normally moves in the direction indicated by the associated arrow in the diagram, and the reference character 3 designates a second stretch of track over which trafiic normally moves in the direction indicated in the I drawing by its associated arrow. The tracks 2 and 3 are so arranged that trafiic movements over a portion of one track will conflict with traffic movements over a portionof the other track. As herein shown, track 3 converges into and joins. track 2, but it will be understood, of course, that my invention is not limited to the particular track layout shown for the purpose of illustration.

The reference characters 2S and 3S designate railway traffic controlling signals, signal 28 beingprovided for track 2 and signal 3S- being provided for track 3, each signal controlling traffic movements over its associated track toward the junction of the two tracks.

Tracks 2 and 3 are each provided in the usual manner with an approach section 2T or 3T, respectively, each terminating at the fouling point of the two tracks, that is, at the point at which traffic movements on the one track will interfere with tramc movements on the other. A control section IT is also provided and includes the junction points of; the two tracks, extending therefrom along each track so as to adjoin each approach section. Each of the sections is provided in the usual manner with a track circuit, relays ITR, 2TR and 3TB being included in the track circuits for sections IT, 2T and 3T, respectively. As indicated in the drawing, a spring switch is preferably located at the junction points of tracks 2 and 3 to permit traffic from either track to pass the junction point of such tracks.

The reference character FR designates a polarized signal selecting relay. Relay FR is energized with current of normal or reverse polarity over four circuits each of which will be pointed out hereinafter. At this time, however, it should be pointed out that when relay FR is energized with current of normal polarity, its contact member 4 is then operated to its normal position wherein normal polar contact 4-5 is closed, and that when relay FR is energized with current of reverse polarity, its contact member 4 is operated to its reverse position wherein reverse polar. contact 46 is closed. The parts of relay FR are preferably so proportioned that whenever contact member 4 of relay FR is operated to one position by virtue of current of one polarity, the contact member will remain in that position until the winding of relay FR is energized by current of the other polarity to thereby operate contact member 4 to its other position.

The reference character 2BR designates a signal control relay provided for signal ZS, and the reference character 3BR designates a signal control relay provided for signal 35. Each relay ZHR and 3HR is provided with a pick-up circuit.

governed by relay FR, and which circuits will be pointed out in detail presently. At this time, however, it should be pointed out that the pickup circuit for relay 2I-IR is selected to be completed whenever normal polar contact l5 of relay FR is closed, and that the pick-up circuit for relay 3HR is selected to be completed whenever reverse polar contact 46 of relay FR is closed. Relays 2I-IR and 3HR are each also provided with a stick circuit, and which circuits will be pointed out presently.

Signals 2S and 3S hereinbefore referred to as controlling trafiic operating over tracks 2 and 3, respectively, are preferably of the same type, and may take any one of the many forms of railway signaling devices well known to the art. These signals, however, are herein shown as two-indication signals of the color light type, each comprising a green lamp G and a red lamp R. Signals 2S and 3S are normallydark, but as will appear presently, each signal is adapted to display a green or clear indication when its green lamp G is energized, and a red or restrictive indication when its red lamp R is energized. Each of the signals becomes lighted when the approach section of its associated track becomes occupied, and the particular indication displayed by such signal is determined according as its associated signal control relay is then picked up or released. For example, signal 3S is caused to display its clear indication when lamp G of that signal is energized over a circuit which may be traced from terminal B of a suitable source of current, such as a battery S'l, through back contact 1 of relay ZTR, front contact 3 of relay ZHR, and the filament of lamp G of signal 2S to a midterminal C of battery 27, but it is readily apparent that when relay ZHR is released so that its front contact 8 is opened and its back contact 8 is closed, red lamp R is then energized to cause signal 28 to display its restrictive indication. The circuits whereby signal 38 is caused to display its respective clear or restrictive indication may be traced from terminal B through back contact 9 of relay 3TR, then through front contact I 0 of relay 3I-IR and the filament of lamp G of signal 3S to terminal C, or through back contact IU of relay 3I-IR and the filament of lamp R of signal 38 to terminal C. Battery 31, as shown, is preferably a split battery provided with two outside terminals B and N, respectively, and a midterminal C.

The reference characters ZLSR and BLSR designate trafiic locking relays associated with signal control relays ZHR and SHR respectively. Relay ZLSR is normally energized over a stick circuit which passes from terminal B through back contact H of relay ZHR, front contact 52 of relay ELSR, and the winding of relay ZLSR to terminal C. Relay SLSR is normally energized over a stick circuit which passes from terminal B through back-contact l3 of relay 3HR, front contact Id of relay 3LSR and the winding of 3LSR to terminal C. Relays ZLSR and 3LSR are also each provided with a pick-up circuit, and which circuits will be pointed out presently.

The reference characters l5 and I6 designate manually operable circuit controllers, each of which is herein shown in the form of a push button. Push button I 5 is preferably located adjacent signal 28, while push button [6 is preferably located adjacent signal 3S. The functionof these push buttons will be made clear as the specification progresses.

Having thus described the apparatus embodying my invention, I shall now explain its operation. I shall first assume that the apparatus is in its normal condition as shown in the drawing. In this condition of the apparatus, relays ITR, ZTR, 3TR, ZLSR and SLSR are energized, relays ZHR and 3BR are deenergized, relay FR is also deenergized and its normal polar contact l-5 is close-d, and signals 2S and 33 are in their darkened condition.

With the apparatus in the condition just described, I shall first assume that a train operating on track 2 enters section 2T in approaching the junction with track 3, with the result that relay ZTR isshunted and releases. Relay 2TR in releasing closes its back contact I! and thereby completes a first energizing circuit for relay FR, which circuit passes from terminal B through back contact I! of relay Z'IR, front contact 18 of relay 3TR and the winding of relay FR to terminal C. As may readily be seen from an inspection of the drawing, this first circuit for relay FR will be completed whenever approach section 2T becomes or is occupied during the interval that the other approach section 3T is unoccupied. I shall term the current supplied to relay FR over its first circuit by virtue of the electromotive force across terminals B and C of battery 31, as being current of normal polarity. With relay FR now energized with current of normal polarity, its contact member 5 remains in its normal position to close normal contact G5 and thereby select relay Zl-IR for energization. With relay FZTR released and contact 45 of relay FR closed, relay ZHR becomes picked up over its previously mentioned pick-up circuit, which may be traced from terminal B through front contact H) of relay ITR, normal polar contact l5 of relay FR, front contact 20 of relay SLSR, back contact 2! of relay ZTR and the winding of relay 2BR to terminal C. Also, with relay ZI-IR. picked up to close its front contact 8, and with relay 2TR released so that its back contact I is closed, the circuit previously traced for lamp G of signal 2S is now completed whereby that signal is caused to display its clear indication.

Relay ZHR in picking up closes its front contact 25 to thereby complete its previously mentioned stick circuit, which passes from terminal B through contact 22 of push button 5, contact 23 of push button l5, front contact 24 of relay lTR, front contact 25 of relay 2I-lR, back contact 2| of relay ZTR and the winding of relay ZHR to terminal C. Relay 2HR in picking up also opens its back contact II, thereby opening the previously traced stick circuit for relay ELSR with the result that relay ZLSR releases, but at this time this action of relay 2LSR serves no useful purpose.

With signal 25 now displaying its clear indication, the train on track 2 is signaled to proceed across the junction of tracks 2 and 3. When the train enters section IT, relay I TR is shunted and releases to open its front contacts l9 and 24, thereby opening respectively the previously traced pick-up and stick circuits for relay ZHR, with the result that relay 2HR releases and closes its back contact 8 to control signal 28 to its restrictive indication. This indication will be displayed by signal 2S until such time as the train vacates section 2T and relay 2TR picks up to open its back contact I, whereupon signal 28 becomes dark.

The previously mentioned pick-up circuit for relay ZLSR also is completed when relay 2I-IR releases; so that relay 'ZLSR. ispicked' up and closes its front contact I2 to thereby complete 1 its stick circuit, which circuit holds that relaynormally energized. This pick-up circuit for relay ELSE may be traced. from terminal 5 through back contact H of relay 2%, back contact 29 of relay iTR. (which contact has in multiple therewith contact 36 of push button it), and the winding of relay ZLSR to terminal G.

Then when the train vacates section IT and relay 5TB picks up, the apparatus is restored to its normal condition. I

I shall now assume that, with the apparatus in the condition just described, a train operating on track 3 enters approach section 3T so that relay 3TB is shunted and releases to complete at its back contact It a second energizing circuit for relay FR. This second circuit may be traced from terminal N through front contact 28 of relay 2TB, back contact it of relay 3TH, and the winding of relay FR, to terminal C, and this circuit, as can readily be seen from an inspection of the drawing, will be completed whenever approach section 3T becomes or is occupied during the interval that the other approach section 2T is unoccupied. The polarity of current now supplied to relay FR by virtue of the electromotive force across terminals N and C of battery 31, I shall term reverse polarity. With relay FR, energized by current of reverse polarity, its polar armature 3 is shifted to its reverse position wherein reverse polar contact ifi is closed to complete the previously mentioned pick-up circuit for relay BHR. (which passes from terminal B through front contact #5 of relay iTR, reverse polar contact =i$ of relay FR, front contact 3| of relay ELSE, back contact 32 of relay 3TB and the Winding of relay 321R to terminal C), so that relay 3BR picks up, thereby opening its back contacts ill and I3 and closing its front contacts if} and 33'. The closing of front contact 33 of relay 3BR. coinpletes its previously mentioned stick circuit, which passes from terminal B through contact 22 of push button it, contact 23 of push but= ton 55, front contact 24 of relay ITR, front contact 33 of relay back contact 32 of relay 5TB, and the winding of relay 3BR, to terminal 0'. The closing of front contact if) of relay SHE.

completes the previously mentioned energizing circuit for lamp G of signal 3S whereupon that signal displays its clear indication, and the opening of back contact iii of relay SHE interrupts the stick circuit for relay IELSR whereupon the latter relay releases.

When the train operating on track 3 enters section lT in response to the clear indication displayed by signal 38, relay ITR is released to open at its front contacts i9 and 24, respectively;

the previously traced pickup and stick circuits for relay 31- 3.. Relay 'SHR is thus deenergized and releases to close its back contacts iii and I3, back contact it of relay 3HR. completing the energizing circuit for lamp R of'signal 38 whereupon that signal'displays its restrictive indica-' tion until such time as the train vacates section 3T and relay 3TB becomes reenergized to open its back contact 9. The closing of back contact i3 of relay 3H3. completes the previously mentioned pick-up circuit for relay 3LSR, and which circuit may be traced from terminal B through back contact 13 of relay SHR, back contact of relay iTR (which contact has in multiple therewith contact 35 of push button l5), and

- the winding of relay BLSR to terminal C. Relayand thereby'complete its stick circuitwhich holdsthat relay normally energized. Then, when the train vacates section IT, relay lTR picks up. Relays lT'R, ZTR, 3TH, ZLSR and 3LSR arenovv energized, relays ZI-IR and SEE are deenergized, relay PR is also deenergized, and since it was last energized by current of reverse polarity,re-' verse polar contact 4-6 of relay FR is now closed.

I shall now explain the manner in which the apparatus embodying my invention functions to control signals ZS and 3S'so that trains on each track are permitted to alternately enter the control section IT when both approach sections are concurrently occupied. To illustrate the above operation, I'shall assume that with the apparatus in the condition above described, a first train, operating on track 2, enters approach section 2'1, and that prior, to the time that such first train enters control section iT a second train, operating on track 3, enters approach section ST and a third train, operating on track 2, enters approach section 2T. Thus, both approach sections ET and 3T are concurrently occupied by at least one train, section 2T now being occupied by two trains and section 3T being occupied by one train.

The entrance of the first train on section 2T will select signal ES to display its clear indication to thereby establish priority for track 2, in the ianner pointed out in detail heretofore. That is, the release of relayZTR establishes the previously mentioned first circuit for relay FR, whereupon that relay becomes energized by current of normal polarity to shift its polar contact member 9 to its normal position. In this position of contact member 4, the normal polar contact i-b' of relay FR is closed to complete the pickup circuit for relay ZI-IR, whereupon relay ZHR picks up to control signalZSto its clear indication. ReIay'ZI-IR also opens the stick circuit for relay ELSE so that the latter relay releases.

The entrance of the second train upon section tTwill now control the associated signal to prevent trafiic'movements on track 3 from interfering or conflicting with the priority of movement established for track 2, and will also condition signal selection relay FR so that priority of traffic movement'will be established for track 3 after the first train has operated through control' section iT'. Relay ER is conditioned at this time for the above mentioned operation over a third energizing circuit, which may be traced from terminalN through front contact tt'of relay SLS-R, back contact 21 of relay ZLSR, back contact 28 of relay 2TB, back contact 58 of relay 3TB, and the winding of relay FR to terminal (3. As is readily apparent from an inspection of the drawing, this third circuit will be completed whenever approach section 3T becomes or is cocupied during the interval that the apparatus is controlled by trafiic conditions upon track 2 to cause signal 2S to display its clear indication and thereby grant priority of traffic movement to track 2. The current supplied to relay FR over its third circuit is of reverse polarity, with the result that'relay FR shifts itspolar contact member 4 to its reverse position. In this posi tion of contact member 4, normal polar contact 4'-5 is opened to interrupt at that point the pick-up circuit for relay ZHR (which is now retained energized over its stick circuit), and reverse polar contact t$ is now closed to select and prepare the pick-up circuit for relay SHR. This latter pick-up circuit, however, is open at front contact 3| of the traffic locking relay ZLSR, which relay was released, as was pointed out previously, in response to the energization of signal control relay ZHR, so that trafic conditions upon section 3T will not at this time interfere with the previously established priority for track 2.

The releasing of relay STR in response to the entrance of the second train upon section 3T will also complete the energizing circuit for lamp R of signal 38, with the result that signal is is caused to display its restrictive indication to track 3.

The entrance of the third train upon approach section 2T will have no-eifect upon the operation of the apparatus at this time, since the first train is assumed to be still entirely within section ET, and the apparatus has already established traflic priority to track 2. However, when the first train vacates section 2T, the presence of the third train upon section 2T will then cause signal 28 to display its lighted restrictive indication, as Will be made clear presently.

The entrance of the first train upon control section ET in response to the clear indication displayed by signal 25, results in relay ITR releasing to open the stick circuit for relay ZHR, whereupon the latter relay releases. Relay ZHR in releasing completes the energizing circuit for lamp R of signalZS to cause that signal to display its restrictive condition,v and also completes thepick-up circuit for relay ZLSR. Relay ZLSR then picks up to close its stick circuit at its front contact I2, and also closes its front contact 3| to prepare the pick-up circuit for relay 3HR, but this latter pick-up circuit is now open at front contact I of relay ITR so that relay BHR at this time remains released. At this time, therefore, both approach sections 2T and 3T are occupied, control section IT is also occupied, and signals 28 and 38 display their respective restrictive indications to prevent trafiic movements from the approach sections into the occupied control section. Signal 2S continues to display its lighted restrictive indication after the first train has vacated section 2T, since it has been assumed that section ET is now occupied by the third train, and with relays 2TR and ZHR released, signal 28 is caused to display its lighted restrictive indication.

Vfhen the first train vacates section IT, the apparatus then operates to establish trafiic priority to track 3T so that the second train, operating on track ET, is permitted to operate past the conflicting track portions of tracks 2 and 3. Furthermore, the apparatus also functions to condition the signal selection relay FR so that traffic priority will again be established for track 2 after the train on track 3 has operated through the control section IT. The above mentioned operation of the apparatus is effected by the reenergization of relay ITR in response to the first train vacating section IT, since front contact I9 of relay ITR then closes to complete the pickup circuit for relay 3HR. The energization of relay SHR controls signal 38 to its clear indication to establish traffic priority to track 3, and also controls traflic locking relay 3LSR to its released condition by opening the stick circuit of,

the latter relay. The releasing of relay 3LSR now establishes a fourth energizing circuit for relay FR to thereby condition the latter relay so that priority of traffic movement will again be established for track 2 after the train on track 3 operates past the control section IT. This fourth energizing circuit for relay FR passes from terminal B through back contact 34 of relay 3LSR, front contact 21 of relay 2LSR, back contact 28 of relay ZTR, back contact I8 of relay 3TB, and the winding of relay FR to terminal C. As may readily be seen from an inspection of the drawing, this fourth circuit will be completed whenever approach section 2T becomes or is occupied during the interval that the apparatus is conditioned by traffic conditions on track 3 to cause signal 3S to display its clear indication and thereby establish trafiic priority to track 3. The current now supplied to relay FR over its fourth circuit is of normal polarity, so that relay FR now operates its contact member 4 to its normal position, thereby opening reverse polar contact 4-6 ofrelay FR to interrupt at that point the pickup circuit for relay SHR (which relay is now retained energized over its stick circuit) and closing normal polar contact 3-5 to select and prepare the pick-up circuit for relay ZHR. This latter relay, however, remains released since its pick-up circuit is open at front contact 20 of traflic locking relay 3LSR, which relay was in turn released in response to the energization of relay 3I-IR so that traffic conditions upon track 2 will not at this time effect the-traffic priority established for track 3.

When the second train enters section iT in response to the clear indication displayed by signal 38, relay iTR becomes released and opens the stick circuit for relay SHR. Relay SHR then releases to control signal 38 to display its restrictive indication, and also completes the pick-up circuit for relay 3LSR, whereupon the latter relay picks up to close its front contact I4 and thereby oomplete its stick circuit which holds that relay normally energized. The closing of front contact 20 of relay SLSR does not at this time complete the pick-up circuit for relay ZHR, since this latter circuit is now open at front contact I9 of relay ITR. 'Since it has been assumed that only one train is operating over track 3, it follows that when that train vacates section 3T, relay 3TB, then picks up to open the energizing circuit for signal 3S and thereby control that signal to its darkened condition. It is readily apparent, however, that if section ST is now occupied by another train, signal S then will be controlled to its lighted restrictive indication.

When the second train vacates section IT, the apparatus will then be controlled so that trafiic movements are permitted from section 2T into section IT. This operation of the apparatus is effected when the second train vacates section IT since relay I TR then becomes reenergized and closes its front contact I9 to thereby complete the pick-up circuit for relay ZI-IR, whereupon relay ZHR picks up to control signal 28 to its clear indication to thereby establish priority of move-- ment for track 2. The further operation of the apparatus in response to the third train entering and passing through control section IT in response to the clear indication displayed by signal is under the above conditions, will be substantially similar to the operation of the apparatus first described for a single train operating along track 2, and further detailed explanation is deemed unnecessary.

From the foregoing description, it is readily apparent that when the control section and both approach sections are unoccupied, the entrance of a train upon either one of the approach sections causes the signal associated with that section to display its proceed indication to grant priority of trafiic movement to trafiic operating upon that particular track. It is further apparent that when the apparatus is controlled by traific conditions in either one of the approach-sections so that priority is established for one track, the entrance of a train upon the approach sec-- tion of the other track then causes the signal associated with the latter approach section to displayits restrictive indication, thereby preventing any trafiic movements on this other track from interfering or conflicting with the established priority of traffic movements. Furthermore, it is readily apparent that when each of the two approach sections is concurrently occupied by one or more trains, and the apparatus is conditioned to establish traific priority to one track, the apparatus is so controlled by a train operating through the control section H in response to the established trafilc priority as to establish trafiic priority for the other track, regardless of the number of trains then occupying the track for which trafiic priority first was established. It follows, therefore, that priority in traflic movement across the conflicting portions of track is established for either track whenever its associ ated approach section is entered first by a train; that the established priority is maintained as long as that approach section is occupied and the other approach section is unoccupied; and that whenever both track sections are concurrently occupied, trafiic movements are then so controlled as to permit trains on each track to proceed alternately across the conficting portions of track.

Push buttons l and I6, previously referred to as being located adjacent signals 28 and 3S, respectively, are provided to permit the track priority established by trafi'ic conditions upon tracks 2 and 3 to be manually controlled to a different priority. Such manual control of the track priority may be desirable when, after the apparatus has been automatically controlled to establish trafic priority for one track, it is .desired that a train on the other track be granted priority of movement through the control section. In this event, a trainman of the train for which priority of trafllc movement is desired may then operate the push button located adjacent the signal controlling traffic over the track upon which priority is desired, thereby cancelling the established priority and causing the apparatus to contro1 signals is and 3S to effect the desired new priority. For example, assume that both sections ET and 3T are occupied and the apparatus is conditioned to grant priority in traific movement to track 2. Under the conditions just assumed, signal 28 is displaying its clear indication and signal 38 is displaying its restrictive indication. Also under these conditions, relay FR. is controlled in the manner pointed out in detail heretofore so that reverse polar contact 4-6 is closed to condition the apparatus to establish priority in traffic movement to track 3 after a train moves from section 2T through section iT. I

Under the above assumed conditions, if it is desired to operate a train on track 3 across section IT prior to permitting the train on track 2 to operate across section IT, the trainman of the train on track 3 may then operate push button I6 located adjacent signal 38. This operation of push button it opens contact 22 of push button l6 interposed in the stick circuit for relay 2I-IR, whereupon that relay becomes released to control signal 28 to its restrictive indication, thereby cancelling the established traflic priority eiie'cted by ,trafiic operating-over tracks 2 and 3.

Furthermore, theactuation of push button It also closes contact 383 of that push button to thereby close the pick-up circuit for relay ZLSR, whereupon relay ZLSR becomes energized to close its front contact 82 and thereby complete its stick circuit, and also closes its front contact 3! which now completes the pick-up circuit forrelay SHE. 1

Relay SHE inpiclzing up controls signal 38 to its clear indication to thereby establish the desired tramp priorityfor track 3, whereby the train on track 3 is permitted to cross section IT priorto the train on track it crossing that controlsection. Belay til-IR. in pickingup also opens the stick circuit for relay 3LSR, whereupon the latter relay releases to complete the previously traced fourth energizing circuit for relayFR, since both approach sections 2T and ST are now occupied and the apparatus is conditioned to establish trafic priority to track 3.

With the apparatus now controlled to thevdesired priority, operation of the train on track 3 through control section IT will automatically establish trafiic priority to track-2 in the manner previously pointed out indetail.

Similar control of signals ZS and 3S to grant priority to track 2 when both approach sections are occupied and the apparatus is conditioned to Although I have herein shown and described only one form of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

claim is: H 1. In an automatic railway interlocking system, in combination, two stretches of railway track each having traflic normally operating-in but a single direction thereover, said tracksbeing so arranged that traflic movements over a portion of either track will conflict with trafiic -movements over a portion of the other track, s'aiditwo tracks being provided with a common control section, said control section including the track portions of each track over which traflic movements interfere with traific movements on the other track, each .said track also being provided with an approach section located in apsection being provided :with a signal governing Having thus described my invention, what l .proachof said control section,-.each said approach r Ltrafiic movements from the associatedapproach section into said control section, each said approach section having a signal control relay governing the-associated signalof thatsection, a signal selecting relay operable to a first or to a second position, circuit means responsive to traific conditions in said control section for controlling each of said signal control relays, said circuit .means being governed by said signal selecting relay and being effective to control a first or a second of said signal control relays according as said signal selecting relay is in its respective first or second position, means responsive to traific conditions in each of said approach sections and effective whenever either one of the approach sections becomes occupied during the interval that the other approach section, is unoccupied for controlling the position of said signal selecting relay to select the signal control relay associated with said one approach section for control by said circuit means, and means responsive to traffic conditions in both said approach sections, operative whenever both said approach sections are concurrently occupied and one of said two signal control relays is controlled, for controlling the position of said signal selecting relay to select the signal control relay of the other approach section for control by said circuit means, whereby alternate trafiic movements from each approach section through said control section are permitted when each approach section is concurrently occupied irrespective of the number of trains in each of saidapproved sections.

2. In an automatic railway interlocking system, in combination, two stretches of railway track each having tramc normally operating in but a single direction thereover, said tracks being so arranged that traffic movements over a portion of either track will conflict with trafiic movements over a portion of the other track, said two tracks being provided with a common control section, said control section including the track portions of each track over which trafi'ic movements interfere with traffic movements on the other track, each said track also being provided with an approach section located in approach of said control section, each said approach section being provided with a signal governing traflic movements from the associated approach section into said control section, means responsive to trafiic conditions in said approach sections and eiTective whenever either one of said approach sections is occupied and the other approach section is unoccupied for controlling the signal associated with said one approach section to permit trafiic movements from said one section through said control section, and means responsive to trafiic conditions in both said approach sections, operative whenever both said approach sections are occupied and neither one of said signals is controlled to permit trafic movements through said control section, for rendering the other signal capable of being controlled to permit traiiic movements from its associated approach section into said control section, said last mentioned means being governed by traflic conditions in said control section and being effective to permit traflic movements alternately from each approach section through said control section when both said approach sections are concurrently occupied.

3. In an automatic railway interlocking system, in combination, two stretches of railway track each having traffic normally operating in but a single direction thereover, said tracks being so arranged that traflic movements over a portion of either track will conflict with traific movements over a portion of the other track, said two tracks being provided with a common control section, said control section including the track portions of each track over which traffic movements interfere with traffic movements on the other track, each said track also being provided with an approach section located in ap-' proach of said control section, each said approach section being provided with a signal governing traffic movements from the associated approach section into said control-section, acontrol relay for each signal, a traffic locking relay for each signal governed by the associated control relay, a signal selecting relay operable between a first and a second position, control means for energizing each control relay governed by the traflic locking relay of the other control relay, said control means being responsive to trafiic con-ditions in the associated approach and in said control section and being selected to energize a first or the second of said control relays according as said signal selecting relay is in its respective first or second position, circuit means responsive to traflic conditions in said approach sections, operative whenever either one of said approach sections is occupied and the other section is unoccupied, for causing said signal selecting relay to operate to its particular position wherein the control relay of said one approach section is selected for energization by said control means, and other circuit means governed by said trafiic locking relays and cooperating with the first mentioned circuit means, effective whenever both approach sections are occupied and either one of said control relays is energized, for causing said signal selecting relay to operate to its particular position wherein the other one of said control relays is selected for energization by said control means.

4. In an automatic railway interlocking system, in combination, two stretches of railway track each having traffic normally operating in but a single direction thereover, said tracks being so arranged that trafl'ic movements over a portion of either track will conflict with trafiic movements over a portion of the other track, said two tracks being provided with a common control section, said control section including the track portions of each track over which traflic movements interfere with trafiic movements on the other track, each said track also being provided with an approach section located in approach of said control section, an approach track relay for each approach section and a control track relay for said control section, a signal for each approach section, a signal control relay for each approach section for controlling the associated signal, a polarized relay operable to one position or to another position, a pick-up circuit for each signal control relay governed by the other signal control relay and including a front contact of said control track relay and a back contact of the associated approach track relay, said pick-up circuits each being governed by said polarized relay and being elfective to energize one or the other of said signal control relays when and only when said polarized relay is in its respective one or its other position, a stick circuit for each signal control relay including a front contact of said control track relay and a back contact of the associated approach track relay, circuit means governed by said approach track relays, operative whenever either one of said approach sections is occupied and the other approach section is unoccupied, eiiective to operate said polarized relay to its one or its other position according as one or the other of said approach sections is then occupied, other circuit means governed by said signal control relays and cooperating with the first mentioned circuit means, operative whenever both said approach sections are occupied and either one of said signal control relays is energized, for operating said polarized relay to its particular position wherein the pick-up circuit for the other one of said signal control relays is prepared, whereby control of said signals-is established to permit traflic movements alternately from each approach section through said control section in the event that both approach sections are concurrently occupied irrespective of the number of trains in each approach section.

5. In an automatic railway interlocking system, in combination, two stretches of railway track each having traffic normally operating in but a single direction thereover, said tracks being so arranged that traffic movements over a portion of either track will conflict with traffic movements over a portion of the other track, said two tracks being provided with a common control section, said control section including the track portions of each track over which traffic movementsinterfere with traiflc movements on the other track, each said track also being provided with an approach section located in approach of said control section, an approach track relay for each approach section and a control .track relay for said control section, a signal for each approach section, a signal control relay for each signal, a signal selecting relay operable to one-or another of two positions, a pick-up circuit for each signal control relay governed by the other signal control relay and by the associated approach track relay and said control track relay, said pick-up circuits being further governed by said signal selecting relay in such manner that one signal control relay will be energized only if said signal selecting relay is in its one position and the other signal control relay will be energized only if said signal selecting relay is in its other position, astick circuit for each signal control relay governed by the associated approach track relay and said control track relay, circuit means governed solely by said approach track relays and effective whenever either one of said approach sections is occupied and the other approach section is unoccupied for causing said signal selecting relay to operate to its particular position wherein the pick-up circuit of the associated signal control relay is conditioned to energize that signal control relay, and other means governed by said signal control relays and cooperating with said circuit means whenever both approach sections are occupied and either one of said signal control relays is energized, for causing said signal selecting relay to operate to its particular position wherein the pick-up circuit of the other one of said signal control relays is conditioned to energize said other signal control relay, whereby trains are controlled by said signals for alternate movements from each track through said control section whenever both approach sections are concurrently occupied irrespective of the number of trains occupying each approach sponsive to tralnc conditions in said-approach sections and controlled by trafic movements through said control section for automatically controlling said signals to permit alternate trafficmovements from said approach sections when such sections are concurrently occupied irrespective of the number of trains in each of said approach sections,

'7. In an automatic railway interlocking system, in combination, two stretches of railway track arranged in such manner that traffic move ments over a portion of either track will conflict with traffic movements over a portion of the other track, a control section common to said two tracks and including the conflicting traiiic portions of such tracks, two signals one for each of said tracks for governing traflic over the conflicting portion ofthe associated track, an approach section foreach signal, and means responsive to traflic conditions insaid approach sections and automatically controlled by traillc movements through said control section for alternately clearing first one and then the other of said two signals whereby to permit trafiic movements alternately from first one and then the other of said two approach sections when such sections are concurrently occupied regardless of the number of trains occupyingeach of said approach sections. I

8. In an automatic railway interlocking system, in combination, two stretches of railway track arranged in such manner that trafiic movements over a portion of either track will conflict with traffic movements over a portion of the other track, a control section common to said two tracks and including the conflicting traffic portions of such tracks, two signals one for each of said tracks for governing traffic over the conflicting portion of the associated track, an approach section for each signal, and means responsive to traffic con- .ditions in said approach sections for clearing the one signal associated with the one of said two approach sections first to become occupied by a train and automatically controlled by trafiic:

such tracks, two signals one for each of said tracksfor governing traihc over the conflicting portions of the associated track, an approach section for .each signal, circuit means responsive to trafiic .conditlons in said approach sections and automatically controlled by trafiic movements through said control section for controlling said signals to permit alternate trafiic movements from said approach sections when such sections are concurrently occupied irrespective of the number of trains occupying each of said approach sections, and manually operable means for modifying the control exerted by said circuit means over said signals whereby to permit successive movements from either of said approach sections when such approach sections are concurrently occupied.

10. In an automatic railway interlocking system, in combination, two stretches of railway track arranged in such manner that trafiic movements over a portion of either track will conflict with trafiic movements over a portion of the other track, a control section common to said two tracks and including the conflicting traflic portions of such tracks, two signals one for each of said tracks for governing traffic over the conflicting portion of the associated track, an approach section for each signal, circuit means responsive to traffic conditions in said approach sections for clearing the one signal associated with the one of said two approach sections first to become occupied by a train and automatically controlled by trafiic movements through said control section for alternately clearing said two signals to permit trains to move alternately from each approach section through said control section when both approach sections are concurrently occupied, and manually operable means for modifying the control exerted by said circuit means over said two signals whereby to permit successive movements from either of said two approach sections when such approach sections are concurrently occupied.

11. In an automatic railway interlocking system, in combination, two stretches of railway track arranged in such manner that traflic movements over a portion of either track will conflict with tramc movements over a portion of the other track, a control section common to said two tracks and including the conflicting trafiic portions of such tracks, two signals one for each of said tracks for governing trafiic over the conflicting portion of the associated track, an approach section for each signal, circuit means responsive to trafiic conditions in said approach sections for clearing the one signal associated with the one of said two approach sections first to become occupied by a train and automatically controlled by traflic movements through said control section for alternately clearing said two signals to permit trains to move alternately from each approach section through said control section when both approach sections are concurrently occupied, and manually operable means effective when both of said approach sections are occupied and either one of said two signals is cleared by said circuit means for setting that one signal to stop and for clearing the other of said two signals.

12. In an automatic railway interlocking system, in combination, two stretches of railway track arranged in such manner that traffic movements over a portion of either track will conflict with traflic movements over a portion of the other track, a control section common to said two tracks and including the conflicting portions of such tracks, two signals one for each of said tracks for governing traflic over the conflicting portion of the associated track, two control relays one for each signal, an approach section for each signal, signal selecting means eifective to select for control one or the other of said two control relays, means responsive to trafiic conditions in said approach sections for controlling said signal selecting means to select the one of said two control relays associated with the signal of the section first to become occupied by a train and automatically controlled by traflic movements through said control section for controlling said signal selecting means to select said two control relays alternately, whereby trains from first one and then the other of said two approach sections alternately are permitted to proceed through said control section when both said approach sections are occupied.

13. In an automatic railway interlocking system, in combination, two stretches of railway track arranged in such manner that trafiic movements over a portion of either track will conflict with traffic movements over a portion of the other track, a control section common to said two tracks and including the conflicting portions of such tracks, two signals one for each of said tracks for governing traflic over the conflicting portion of the associated track, two control relays one for each signal, an approach section for each signal, a polarized signal selecting relay operable between a first position and a second, circuit means controlled by said polarized relay for selecting a first or a second of said two signal control relays for control according as said polarized relay is in its first or second position, and other circuit means responsive to trafiic conditions in said approach sections for operating said polarized relay to its particular position wherein is selected the one of said two control relays associated with the signal of the approach section first to become occupied and controlled by traffic movements through said control section for reversibly operating said polarized relay to select said two control relays alternately, whereby alternate tranic movements from first one and then the other of said two approach sections are permitted when such sections are concurrently occupied.

14. A railway interlocking system of the class wherein signals governing traffic movements over two tracks having conflicting trafiic portions are alternately cleared automatically by trafiic m0vements over the conflicting portions of such tracks when approach sections provided for each track are concurrently occupied, characterized by the provision in such system of a polarized signal selecting relay reversibly operated by circuit means responsive to traffic conditions in the said approach sections and in said conflicting traflic portions of said two tracks, and controlling circuit means for selecting one or the other of said two signals to be cleared according as said polarized relay is in one or another of its two positions.

JOHN M. PELIKAN. 

